Study design

An overview of the study design can go in the aim, legend or as a separate section. However, it can save space and enhance the readers understanding of the experiment, if it is presented early on i.e. at the end of the aim or in a separate section after the aim.

Typically, the information in the study design should tell the reader:

  1. Information about sample and sampling (size, characteristics etc. of sample, randomness of sampling etc.).
  2. General information about how the experiment was carried out and the conditions under which the data were collected. This information should not be repeated in other parts of the report that deal with methodology.

The study design must be clear and accurate.

For more explanation, click on the highlighted text example taken from a report on 'Varying the Dietary Intake of Cholesterol May Cause Changes in Plasma Cholesterol Concentration in Middle-Aged Subjects'

Study Design

Subjects were picked in an age range 49-58 years (n=8, 6 male and 2 female) and randomly allocated to either a high cholesterol diet (foods suggested included meat, dairy products, offal) or a low cholesterol diet (mainly plant derived foods) to be consumed over a 12 week period. Subjects were tested for blood cholesterol concentration prior to beginning their diets and then at Week 6 and Week 12.

This information tells the reader about the sample (size, sex, age range) and sampling (subjects chosen in certain age range, random allocation to high or low cholesterol diet).

This information tells the reader the overall methodology of the experiment (its duration and when cholesterol measurements were taken).

Examine the Study Design from a student's report entitled: 'Varying the Dietary Intake of Cholesterol May Cause Changes in Plasma Cholesterol Concentration in Middle-Aged Subjects'.

All of the information given is important. However, if you were the lecturer, which 2 pieces of extra information listed in A, below, would you choose to award bonus marks for? Click the Bonus marks button if you want to allocate these marks to a piece of information and then click the Submit button.

Study Design

Table 1. Demographic characteristics of study participants.

6 subjects (4 male and 2 female) were recruited. No subjects reported cardiovascular problems or hypercholesterolemia.

Subjects were randomly allocated to a nominally high or low cholesterol diet. The nature and quantity of the foods consumed was at the discretion of each individual. One of the subjects in the high-cholesterol group was rejected from the study after admitting non-compliance.

  Mean ± SEM Range
Age (years) 53.0 ± 1.1 49 − 58
Body Mass Index (kg/m2) 26.0 ± 1.1 21 − 32

Subjects were randomly allocated to a nominally high or low cholesterol diet. The nature and quantity of the foods consumed was at the discretion of each individual. One of the subjects in the high-cholesterol group was rejected from the study after admitting non-compliance.

A

1. Mean age

Bonus Marks

2. Body mass data

Bonus Marks

3. One of the subjects was rejected from the high cholesterol group

Bonus Marks

4. Relevant medical data

Bonus Marks

5. Diet choices were up to the individual

Bonus Marks

Information in 2 and 4 would receive bonus marks.

  1. Blood cholesterol levels are influenced by body mass, so showing the average body mass index of the sample and its range is important.
  2. Providing relevant medical data about the sample is important as it shows that subjects do not have a prior medical condition which could lead to abonormally high levels of blood cholesterol.

What is the advantage of using a table to show subject characteristics? Which of the advantages listed in B is a real advantage. Indicate what you think are real advantages by clicking either the Agree or Disagree button and then click the Submit button.

B

1. It looks more scientific

agree | disagree

2. It is more accurate

agree | disagree

3. It allows the data to be read at a glance

agree | disagree

4. It allows more numerical subject data to be entered with ease
   (e.g. : mean age, body mass index)

agree | disagree
» Screen 1 | 2 | 3 | 4 | 5 | Next: Scientific language